[$] daxctl() — getting the other half of persistent-memory performance

Persistent memory promises high-speed, byte-addressable access to storage,with consequent benefits for all kinds of applications. But realizing thosebenefits has turned out to present a number of challenges for the Linuxkernel community. Persistent memory is neither ordinary memory norordinary storage, so traditional approaches to memory and storage are not always well suitedto this new world. A proposal for a new daxctl() system call,along with the ensuing discussion, shows how hard it can be to get the mostout of persistent memory.